Carburetor



Sept. 30 1924.

F. H. ARNoTT CARBURETOR Filed Aug. 9, 1921 Patented Sept. 30, 1924,,

FRANK HADFIELD Alt-NOTE, 0'33 LONDON, ENGLAND.

CABBURETOR.

Application filed August 9, 1921. Serial No. 490,986.

To all whom it may concern.

Be it known that I, FRANK HADFIELD An- NOTT, a subject of the King ofGreat Britain and Ireland, and residing at Willesden Green, London, N.W. 10, England, have invented certain new and useful Tmprovements in andRelating to Carburetors, of which the following is a specification.

This invention relates to carburetors for internal combustion enginesand more particularly to the type wherein the main supply of air isautomatically controlled.

The object of the invention is to provide a carburetor which willdeliver automatically to the engine a correctly proportioned mixture offuel and air at all degrees of opening of the throttle valve.

The invention consists in the combination and arrangement of parts anddetails of construction hereinafter described and claimed, it beingunderstood that changes in the embodiment of the invention hereindisclosed may be made within the scope of the claim, without departingfrom the spirit of the invention.

An example of a carburetor according to the invention is illustrated inthe accompanying drawings, of which:

Figure 1 is a diagrammatic sectional elevation, and

Figure 2 is a modification of the spring control mechanism of Figure 1.

As shown in the drawings, the carburetor includes a float chamber Ahaving a known constant level device for the fuel, sealed from theatmosphere, and integral with an extension B. The upper part of B has acylindrical bore which is closed at the top by a bobbin-shaped plug Cscrewed or otherwise fastened therein. This plug is bored axially andforms a guide for a push rod D whose upper end extends through the plugC and whose lower end bears upon the piston-shaped head G of a taperedneedle valve H.

The piston G slides freely in the cylindri cal bore of B and thecombination acts as a d ashpot to steady the movement of the neodlevalve in a jet orifice P formed in the lower part of B. This lower partof B is formed with a cylindrical outer surface surrounding the jetorifice P.

An extension W, surrounding and coaxial with the cylindrical lower partof B, forms a mixing chamber and a pipe V leads from this chamberthrough a throttle valve T to the engine. The lower end of the chamber Whas'an internally threaded orifice into which an externally threadedtubular part M. is fitted. The upper inner surface of the part M ischamfered conically and provides a seat for a combined air and fuelvalve K. This valve is formed as a hollow cylinder open at its upper endand closed at its base excepting for a series of holes or ports L. Adownward projecting part of the needle valve H extends beyond theorifice P to a point adjacent to the base of the valve K and exactadjustment of the relative positions of the valve K and needle valve Hmay be accomplished by adjusting the part M in which the valve K seatsupwardly or downwardly. A short parallel. portion of the valve K ofslightly reduced diameter below the ports L is a sliding fit in theparallel part of the part M and a short conical face corresponding tothe chamfer of the part M extends from the reduced parallel part to thefull outer diameter of the valve K. The valve K is arranged to extendover and slide upon the cylindrical outer surface of the lower part of Band forms a chamber surrounding the jet orifice P. This chamber isconnected directly with the air space in the top of the float chamber Aby an air passage S passing through the body of the part B into thewaist of the plug C and thence through the wall of the float chamber A.A passage J connects the lower part of the float chamber A and the lowerpart of the cylindrical bore of It follows from this construction thatthe pressure in the upper part of the float chamber is equal to that inthe chamber surrounding the fuel jet orifice and therefore the pressureof the fuel at the jet orifice is constant and independent of thevarying suction of the engine.

A lever N pivoted at O is caused by the tension of a spring E to bearupon the upper end of the push rod D.

The tension of this spring may be varied by any known construction, suchas a control wire F. In the modification shown in Figure 2 the spring Racts directly upon the piston-shaped head G without the intervention ofthe lever N and the push rod D.

The operation of the device is as follows lVhen the throttle valve T isclosed the valve K is seated on the part M and the needle valve H closesthe orifice P by gravity and the pressure of the spring.

On slightly opening the throttle valve T, engine suction causes thevalve K to rise and open the needle valve H, thus per tting fuel to flowto the interior of the valve K assoon as the lower parallel part of thevalve is raised clear of the part M, while air is sucked through the uaulus between the two couical surfaces or the valve and the part Mrespectivel y and is mixed with the fuelwhich flows from the interior ofthe valve K through the ports L. in initial adjustment of the part M isnecessary in order to obtain the best setting of the relative positionsof the valve l and the needle valve H but when this is obtai: ed thepart is secured from further move ment. It will be seen that furtheropening of the throttle T will result in ahigher mean position of theautomatic valve K with a corresponding effect on the needle valve.Proper proportioning of the needle alve. together with the fact that thepressure of the fuel is independent of the effects of en for the amountof air sucked in.

As the ports L are situated in U 1e narrowest part of the passage forthe incoming; air it will be seen that the greatest possible reductionof pressure existing in the carburetor is available for the atomizationof the fuel.

Having; now described my invention, What I claim as new and desire tosecure by Letters Patent is iii. carburetor of the t -ipe describedincluding in combination a mivin chamben :1 throttle valve between theengine and said misting chamber, a constant level flout chamber sealedfrom the atmosphere, a jet orifice below the level of the fuel in saidfloat chamber. a loaded combined air and fuel valve adrptcd to be openedby engine suction thro said throttle valve, fuel ports in the lower partof said combined valve at the position of greatest restriction of airentering the mixing chamber, and a passage connecting the areasurrounding and acting upon the fuel jet with the upper part of saidfloat chamber.

In testimony whereof I have signed my name to this specification.

FRANK HADFIELD ARNOTT'.

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